Methods of fabricating integrated circuitry and semiconductor processing polymer residue removing solution

ABSTRACT

The invention includes methods of fabricating integrated circuitry and semiconductor processing polymer residue removing solutions. In one implementation, a method of fabricating integrated circuitry includes forming a conductive metal line over a semiconductor substrate. The conductive line is exposed to a solution comprising an inorganic acid, hydrogen peroxide and a carboxylic acid buffering agent. In one implementation, a method of fabricating integrated circuitry includes forming an insulating layer over a semiconductor substrate. A contact opening is at least partially formed into the insulating layer. The contact opening is exposed to a solution comprising an inorganic acid, hydrogen peroxide and a carboxylic acid buffering agent. In one implementation, a semiconductor processing polymer residue removing solution comprises an inorganic acid, hydrogen peroxide and a carboxylic acid buffering agent. Other aspects and implementations are contemplated.

TECHNICAL FIELD

[0001] This invention relates to methods of fabricating integratedcircuitry and to semiconductor processing polymer residue removingsolutions.

BACKGROUND OF THE INVENTION

[0002] Integrated circuitry fabrication in semiconductor processingtypically forms contact openings, passageways or vias through insulatingmaterials for interconnecting different conductive components. Further,integrated circuitry fabrication typically forms conductive metal linesas transistor gate lines or for interconnecting, energizing or accessingdifferent electronic components.

[0003] A typical method of forming contact openings and metal lines isby subtractive etching using one or more masking layers. One exemplarymasking material is photoresist. At the completion of the etching usinga photoresist masking layer, the photoresist is typically etched fromthe substrate and does not constitute a part of the finished circuitryconstruction. In certain instances, the act of etching the photoresistfrom the substrate can leave undesired polymer residue over theconductive lines or within the contact openings. This has becomeparticularly problematic as the dimensions of openings and lines arebecoming ever smaller to enable maximizing circuit density.

[0004] One exemplary process and aqueous solution for removing polymerresidue from a substrate in such instances is described in an article ofMicro, June 2001, entitled “Removing postash polymer residue from BEOLstructures using inorganic chemicals”. Such utilizes a solution composedof sulfuric acid, hydrogen peroxide, hydrogen fluoride and water.

[0005] One material presently finding use in the formation of conductivelines in semiconductor fabrication is elemental aluminum or aluminumalloys. Unfortunately, the sulfuric acid, hydrogen peroxide and hydrogenfluoride solutions presently being used can also significantly etchaluminum and aluminum alloys. Accordingly, care is taken when utilizingsuch solutions to ensure that the substrates are exposed to suchsolutions effective to remove the polymer residue, but not to a degreeto significantly etch aluminum containing lines or other structures onthe substrate. The present method by which this is achieved is in use ofspray-rinse processors which, over a short time interval, spray thesubstrates with the solution. This is rapidly followed by asubstantially pure, de-ionized water rinse.

[0006] While the invention was motivated in addressing the above issuesand improving upon the above-described drawbacks, it is in no way solimited. The invention is only limited by the accompanying claims asliterally worded (without interpretative or other limiting reference tothe above background art description, remaining portions of thespecification, or the drawings), and in accordance with the doctrine ofequivalents.

SUMMARY

[0007] The invention includes methods of fabricating integratedcircuitry and semiconductor processing polymer residue removingsolutions. In one implementation, a method of fabricating integratedcircuitry includes forming a conductive metal line over a semiconductorsubstrate. The conductive line is exposed to a solution comprising aninorganic acid, hydrogen peroxide and a carboxylic acid buffering agent.In one implementation, a method of fabricating integrated circuitryincludes forming an insulating layer over: a semiconductor substrate. Acontact opening is at least partially formed into the insulating layer.The contact opening is exposed to a solution comprising an inorganicacid, hydrogen peroxide and a carboxylic acid buffering agent. In oneimplementation, a semiconductor processing polymer residue removingsolution comprises an inorganic acid, hydrogen peroxide and a carboxylicacid buffering agent.

[0008] Other aspects and implementations are contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

[0010]FIG. 1 is a diagrammatic sectional view of a semiconductorsubstrate fragment at one processing point in accordance with an aspectof the invention.

[0011]FIG. 2 is a view of the FIG. 1 substrate fragment at a processingstep subsequent to that shown by FIG. 1.

[0012]FIG. 3 is a view of the FIG. 2 substrate fragment at a processingstep subsequent to that shown by FIG. 2.

[0013]FIG. 4 is a view of the FIG. 3 substrate fragment at a processingstep subsequent to that shown by FIG. 3.

[0014]FIG. 5 is a diagrammatic sectional view of an alternatesemiconductor substrate fragment at one processing point in accordancewith an aspect of the invention.

[0015]FIG. 6 is a view of the FIG. 5 substrate fragment at a processingstep subsequent to that shown by FIG. 5.

[0016]FIG. 7 is a view of the FIG. 6 substrate fragment at a processingstep subsequent to that shown by FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] This disclosure of the invention is submitted in furtherance ofthe constitutional purposes of the U.S. Patent Laws “to promote theprogress of science and useful arts” (Article 1, Section 8).

[0018] An exemplary method of fabricating integrated circuitry isinitially described with reference to FIGS. 1-4. Referring initially toFIG. 1, a semiconductor substrate is indicated generally with referencenumeral 10. In the context of this document, the term “semiconductorsubstrate” or “semiconductive substrate” is defined to mean anyconstruction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above. Also in the context of this document, the term “layer”encompasses both the singular and the plural unless otherwise indicated.

[0019] In the first-described exemplary embodiments, substrate fragment10 comprises a semiconductor substrate 12 which would typically becomposed of multiple different layers and materials. The initialdiscussion proceeds with exemplary methods of forming a conductive metalline over substrate 12. In the context of this document, a “metal line”is defined as a conductive conduit/interconnect having a length greaterthan its maximum width and thickness and where at least a majority of italong its length consists essentially of “metal”. In the context of thisdocument, “metal” is defined to mean any one or combination of one ormore elemental metals, one or more alloys of at least two elementalmetals, and one or more conductive metal compounds. FIG. 1 depicts threeexemplary metal layers 14, 16 and 18. Exemplary thicknesses are about100 Angstroms, about 3000 Angstroms and about 200 Angstroms,respectively. An exemplary material for layer 14 is titanium. Anexemplary material for layer 18 is titanium nitride. An exemplarymaterial for layer 16 is elemental aluminum and/or an alloy of aluminumand copper (i.e., 99.5 weight percent aluminum and 0.5 weight percentcopper). A patterned carbon containing masking layer 20 is formed overlayers 14, 16 and 18. An exemplary preferred material is photoresistprocessed by any existing or yet-to-be developed photolithographic orother techniques.

[0020] Referring to FIG. 2, layers 14, 16 and 18 have been etched usingmasking layer 20 to form a conductive metal line 22. In one preferredimplementation, metal of the metal line comprises elemental aluminum,aluminum alloy or a combination thereof. In one preferred embodiment, atleast a majority of the metal in the metal line comprises elementalaluminum, aluminum alloy or a combination thereof. In one preferredimplementation, aluminum present in the line is predominately present inat least one of elemental and alloy form. In one preferred embodiment,the conductive metal line consists essentially of metal, for example asshown. An exemplary gas for etching aluminum includes BCl₃, whereasexemplary gases for etching TiN are NF₃ and CF₄.

[0021] The above preferred processing describes but one exemplary andpreferred method of forming a conductive metal line over a semiconductorsubstrate. In certain implementations, any other method of forming aconductive metal line over a substrate is contemplated, for example withor without using a masking layer, and whether existing or yet-to-bedeveloped.

[0022] Referring to FIG. 3, carbon containing masking layer 20 (notshown) has been etched from the substrate. An exemplary method for doingso where the masking layer is photoresist includes O₂ plasma which canbe conducted in situ within the chamber(s) in which the etching wasconducted to produce the exemplary FIG. 2 construction. In but oneexemplary embodiment, at least one of the carbon containing maskinglayer etching (i.e., that which would occur to produce the FIG. 3construction) and the aluminum or other metal comprising layer etching(i.e., that which would occur to produce the FIG. 2 construction) leavesa polymer residue 25 over some portions of conductive line 22. By way ofexample only, FIG. 3 depicts a discontinuous residue 25 forming overline 22. Such might alternately be formed to completely cover thedepicted construction. An example undesired polymer residue which isformed includes carbon and fluorine atoms.

[0023] Referring to FIG. 4, conductive metal line 22 has been exposed toa solution comprising an inorganic acid, hydrogen peroxide and acarboxylic acid buffering agent. In one preferred implementation, suchexposing is effective to remove at least some, more preferably at leasta majority, and most preferably all, of residue 25 from over conductivemetal line 22. Exemplary methods of conducting the exposing includesspraying the substrate, for example in liquid form or in a combinationof gas and liquid. One most preferred exemplary method of exposingcomprises bath immersion. Further and regardless, certain aspects of theinvention contemplate exposing the conductive metal line to a solutioncomprising an inorganic acid, hydrogen peroxide and a carboxylic acidbuffering agent independent of whether polymer residue is formed, andindependent of removing such residue if it is formed.

[0024] Exemplary and preferred inorganic acids include H₃PO₄ and H₂SO₄,with H₂SO₄ being more preferred. Exemplary preferred carboxylic acidbuffering agents include those derived, at least in part, from the groupconsisting of ammonium citrate, ammonium lactate, ammonium oxalate, andmixtures thereof. In one preferred implementation, the solutioncomprises ammonium ions/counterions.

[0025] Preferably, the solution has a pH of from 3.0 to 7.0, with a pHrange of from 3.8 to 4.8 being more preferred. During the exposing, thesolution is preferably at a temperature from 18° C. to 40° C., with anexemplary preferred pressure during exposure being ambient atmosphericpressure. By way of example only, an exemplary preferred exposure timeis anywhere from 30 seconds to 5 minutes.

[0026] In one preferred embodiment, the solution includes HF.

[0027] Exemplary preferred concentrations and ranges are inorganic acidbeing present at from 1.0 weight percent to 15.0 weight percent;hydrogen peroxide being present at from 1.0 weight percent to 15.0weight percent; HF being present at from 0 to 1,000 ppm by weight (with50-200 ppm by weight being more preferred); and with the remainder beingwater. A solution as just described but without any effective carboxylicacid buffering agent typically has a pH below 2.0. A carboxylic acidagent is ideally provided within the solution in a preferred quantityeffective to raise the pH to above 3.0, and more preferably to provide apH range of from 3.8 to 4.8. One exemplary preferred solution into whicha carboxylic acid buffering agent can be provided is DSP+ available fromKanto Corporation of Portland, Oreg. DSP+ is understood to constitute 7weight percent sulfuric acid, 7 weight percent hydrogen peroxide and 100ppm HF, with the remainder at slightly less than 86 weight percent beingwater. In accordance with aspects of the invention, a usable solutionwas created by adding 200 grams/liter of diammonium citrate salt, whichresulted in a stable pH of around 4.

[0028] Again in one preferred embodiment, an immersion bath is createdor otherwise provided containing the above preferred embodimentsolution. A substrate with the conductive metal line is immersed intosuch bath. In one exemplary preferred aspect, polymer residue was formedover the conductive line and the immersion is effective to remove atleast some, and preferably at least a majority, of the residue from overthe conductive line.

[0029] In one reduction-to-practice example, the exemplary FIG. 3construction was created. A bath was provided having the above DSP+ with200 grams/liter of diammonium citrate salt dissolved therein. Suchsolution had a pH of about 4. The solution was provided at ambientpressure conditions and at a temperature of about 30° C. A plurality ofwafers was immersed in the bath for 60 seconds. Control wafers wereprocessed in a bath under the same conditions containing solely DSP+,and another batch of control wafers was not processed to remove anypolymer residue that might have formed. Subsequent identical processingwas conducted on all of the wafers described above. At probe testing,the wafers processed with the above solution in accordance with theinvention outperformed both control groups in terms of yield andpercentage of open structures for 0.12 micron width lines. Further, thecondition of the metal was examined in the DSP+ control group and theDSP+ containing the carboxylic acid buffering agent group. The DSP+processed substrates showed pitting of the exposed aluminum, whereas thecarboxylic acid buffered DSP+ processed substrates showed negligible, ifany, attack on the aluminum.

[0030] It is theorized that the carboxylic acid buffered solution at anappropriate pH, for example of at least 3.0 and more preferably from 3.8to 4.8, passivates the aluminum surfaces to preclude etching of thealuminum.

[0031] In accordance with aspects of the invention, an exemplaryalternate embodiment is described with reference to FIGS. 5-7. FIG. 5depicts a wafer fragment or semiconductor substrate 50. By way ofexample only, such includes a bulk monocrystalline substrate 52 having aconductive diffusion region 54 formed therein. One or more insulativematerials 56 is formed over semiconductor substrate 52. An exemplarypreferred material is borophosphosilicate glass (BPSG) deposited to anexemplary thickness of 5,000 Angstroms.

[0032] Referring to FIG. 6, a contact opening 60 has been at leastpartially formed into insulating layer 56, with the exemplary opening 60being shown formed entirely through insulating layer 56 to exposeexemplary diffusion region 54. Such might be conducted byphotolithographic patterning and etch, or by other existing or yet-to-bedeveloped methods. In one exemplary aspect and as shown in FIG. 6, apolymer residue 64 is shown as having been formed within contact opening60.

[0033] Referring to FIG. 7, contact opening 60 has been exposed to asolution comprising an inorganic acid, hydrogen peroxide and acarboxylic acid buffering agent. All aspects and preferred solutions areas described above with respect to the first described embodiment.Further, certain aspects of the invention contemplate exposure of thecontact opening to such exemplary solution(s) regardless of any polymerresidue formation, and regardless of whether such polymer is removed asa result of the exposing. Exemplary exposing methods include spraying,bath immersion and any other method whether existing or yet-to-bedeveloped.

[0034] The invention also contemplates a semiconductor processingpolymer residue removing solution comprising an inorganic acid, hydrogenperoxide and a carboxylic acid buffering agent independent of themethods described above. Preferably, such a solution has some or acombination of the attributes of the solution(s) used in the methodsdescribed above.

[0035] In compliance with the statute, the invention has been describedin language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that the invention is notlimited to the specific features shown and described, since the meansherein disclosed comprise preferred forms of putting the invention intoeffect. The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of fabricating integrated circuitry comprising: forming aconductive metal line over a semiconductor substrate; and exposing theconductive metal line to a solution comprising an inorganic acid,hydrogen peroxide and a carboxylic acid buffering agent.
 2. The methodof claim 1 wherein the inorganic acid comprises H₂SO₄.
 3. The method ofclaim 1 wherein the inorganic acid comprises H₃PO₄.
 4. The method ofclaim 1 wherein the solution comprises ammonium ions.
 5. The method ofclaim 1 wherein the carboxylic acid buffering agent is derived at leastin part from the group consisting of ammonium citrate, ammonium lactate,ammonium oxalate, and mixtures thereof.
 6. The method of claim 1 whereinthe solution comprises HF.
 7. The method of claim 6 wherein the HF ispresent in the solution at less than or equal to 1000 ppm by weight. 8.The method of claim 6 wherein the HF is present in the solution at from50 to 200 ppm by weight.
 9. The method of claim 1 wherein the solutionhas a pH of from 3.0-7.0.
 10. The method of claim 1 wherein the solutionhas a pH of from 3.8-4.8.
 11. The method of claim 1 wherein the solutionis at a temperature from 18° C. to 40° C.
 12. The method of claim 1wherein the conductive metal line consists essentially of metal.
 13. Themethod of claim 1 wherein metal of the metal line comprises elementalaluminum, aluminum alloy or a combination thereof.
 14. The method ofclaim 1 wherein at least a majority of metal of the metal line compriseselemental aluminum, aluminum alloy or a combination thereof.
 15. Themethod of claim 1 wherein the forming comprises photolithographicpatterning and etch which forms a polymer residue over the conductiveline, the exposing being effective to remove at least a majority of theresidue from over the conductive line.
 16. The method of claim 1 whereinthe inorganic acid comprises H₂SO₄, the carboxylic acid buffering agentcomprises ammonium counterions and the pH is from 3.8 to 4.8.
 17. Themethod of claim 16 wherein the solution comprises HF at less than 1000ppm by weight.
 18. The method of claim 16 wherein the forming comprisesphotolithographic patterning and etch which forms a polymer residue overthe conductive line, the exposing being effective to remove at least amajority of the residue from over the conductive line.
 19. A method offabricating integrated circuitry comprising: forming a conductive metalline over a semiconductor substrate; providing an immersion bathcontaining a solution comprising an inorganic acid, hydrogen peroxideand a carboxylic acid buffering agent; and immersing the substrate withthe conductive metal line within the bath.
 20. The method of claim 19wherein the inorganic acid comprises H₂SO₄.
 21. The method of claim 19wherein the inorganic acid comprises H₃PO₄.
 22. The method of claim 19wherein the carboxylic acid buffering agent is derived at least in partfrom the group consisting of ammonium citrate, ammonium lactate,ammonium oxalate, and mixtures thereof.
 23. The method of claim 19wherein the bath comprises HF.
 24. The method of claim 23 wherein the HFis present in the bath at less than or equal to 1000 ppm by weight. 25.The method of claim 23 wherein the HF is present in the bath at from 50to 200 ppm by weight.
 26. The method of claim 19 wherein the bath has apH of from 3.0-7.0.
 27. The method of claim 19 wherein the bath has a pHof from 3.8-4.8.
 28. The method of claim 19 wherein the bath is at atemperature from 18° C. to 40° C.
 29. The method of claim 19 wherein theforming comprises photolithographic patterning and etch which forms apolymer residue over the conductive line, the immersing being effectiveto remove at least a majority of the residue from over the conductiveline.
 30. The method of claim 19 wherein the inorganic acid comprisesH₂SO₄, the carboxylic acid buffering agent comprises ammoniumcounterions and the bath pH is from 3.8 to 4.8.
 31. The method of claim30 wherein the bath comprises HF at less than 1000 ppm by weight. 32.The method of claim 30 wherein the forming comprises photolithographicpatterning and etch which forms a polymer residue over the conductiveline, the immersing being effective to remove at least a majority of theresidue from over the conductive line.
 33. A method of fabricatingintegrated circuitry comprising: forming a patterned carbon containingmasking layer over an aluminum comprising layer; using the maskinglayer, etching the aluminum comprising layer to form a conductive line;after forming the conductive line, etching the carbon containing maskinglayer from the substrate, at least one of the carbon masking layeretching and the aluminum comprising layer etching leaving a polymerresidue over at least some of the conductive line; providing animmersion bath containing a solution comprising sulfuric acid, hydrogenperoxide, and a carboxylic acid buffering agent; the sulfuric acid beingpresent in the bath at from 1.0 weight percent to 15.0 weight percent,the hydrogen peroxide being present in the bath at from 1.0 weightpercent to 15.0 weight percent, the bath having a pH from 3.0 to 7.0;and after etching the carbon containing masking layer, immersing thesubstrate within the bath under conditions effective to etch at leastsome of the polymer residue from over the conductive line.
 34. Themethod of claim 33 wherein the carbon containing masking layer comprisesphotoresist.
 35. The method of claim 33 wherein the bath comprisesammonium ions.
 36. The method of claim 33 wherein the carboxylic acidbuffering agent is derived at least in part from the group consisting ofammonium citrate, ammonium lactate, ammonium oxalate, and mixturesthereof.
 37. The method of claim 33 wherein the bath has a pH of from3.8-4.8.
 38. The method of claim 33 wherein the bath comprises HF. 39.The method of claim 38 wherein the HF is present in the bath at lessthan or equal to 1000 ppm by weight.
 40. The method of claim 38 whereinthe HF is present in the bath at from 50 to 200 ppm by weight.
 41. Themethod of claim 38 wherein the bath has a pH of from 3.8-4.8.
 42. Themethod of claim 33 wherein the bath is at a temperature from 18° C. to40° C.
 43. The method of claim 33 wherein the aluminum is predominatelypresent in at least one of elemental and alloy forms.
 44. A method offabricating integrated circuitry comprising: forming an insulating layerover a semiconductor substrate, at least partially forming a contactopening into the insulating layer; and exposing the contact opening to asolution comprising an inorganic acid, hydrogen peroxide and acarboxylic acid buffering agent.
 45. The method of claim 44 wherein theexposing comprises spraying.
 46. The method of claim 44 wherein theexposing comprises bath immersion.
 47. The method of claim 44 whereinthe contact opening is formed entirely through the insulating layer. 48.The method of claim 44 wherein the inorganic acid comprises H₂SO₄. 49.The method of claim 44 wherein the inorganic acid comprises H₃PO₄. 50.The method of claim 44 wherein the solution comprises ammonium ions. 51.The method of claim 44 wherein the carboxylic acid buffering agent isderived at least in part from the group consisting of ammonium citrate,ammonium lactate, ammonium oxalate, and mixtures thereof.
 52. The methodof claim 44 wherein the solution comprises HF.
 53. The method of claim,52 wherein the HF is present in the solution at less than or equal to1000 ppm by weight.
 54. The method of claim 52 wherein the HF is presentin the solution at from 50 to 200 ppm by weight.
 55. The method of claim44 wherein the solution has a pH of from 3.0-7.0.
 56. The method ofclaim 44 wherein the solution has a pH of from 3.8-4.8.
 57. The methodof claim 44 wherein the solution is at a temperature from 18° C. to 40°C.
 58. The method of claim 44 wherein the forming comprisesphotolithographic patterning and etch which forms a polymer residuewithin the contact opening, the exposing being effective to remove atleast a majority of the residue from within the contact opening.
 59. Themethod of claim 44 wherein the inorganic acid comprises H₂SO₄, thecarboxylic acid buffering agent comprises ammonium counterions and thepH is from 3.8 to 4.8.
 60. The method of claim 59 wherein the solutioncomprises HF at less than 1000 ppm by weight.
 61. The method of claim 59wherein the forming comprises photolithographic patterning and etchwhich forms a polymer residue within the contact opening, the exposingbeing effective to remove at least a majority of the residue from withinthe contact opening.
 62. A semiconductor processing polymer residueremoving solution comprising an inorganic acid, hydrogen peroxide and acarboxylic acid buffering agent.
 63. The solution of claim 62 whereinthe inorganic acid comprises H₂SO₄.
 64. The solution of claim 62 whereinthe inorganic acid comprises H₃PO₄.
 65. The solution of claim 62comprising ammonium ions.
 66. The solution of claim 62 wherein thecarboxylic acid buffering agent is derived at least in part from thegroup consisting of ammonium citrate, ammonium lactate, ammoniumoxalate, and mixtures thereof.
 67. The solution of claim 62 comprisingHF.
 68. The solution of claim 67 wherein the HF is present in thesolution at less than or equal to 1000 ppm by weight.
 69. The solutionof claim 67 wherein the HF is present in the solution at from 50 to 200ppm by weight.
 70. The solution of claim 62 wherein the solution has apH of from 3.0-7.0.
 71. The solution of claim 62 wherein the solutionhas a pH of from 3.8-4.8.
 72. The solution of claim 62 wherein theinorganic acid comprises H₂SO₄, the carboxylic acid buffering agentcomprises ammonium counterions and the pH is from 3.8 to 4.8.
 73. Thesolution of claim 72 wherein the solution comprises HF at less than 1000ppm by weight.